In vitro simultaneous measurement of refractive index and thickness of biological tissue by the low coherence interferometry

Abstract

We proposed and demonstrated in vitro simultaneous measurement of refractive index and thickness of biological tissue. The technique is based on the low coherence interferometry combined with precise translation stages. Refractive indices were determined with the accuracy of less than 1% for tissue samples of a few hundred micron thickness, including chicken tissue, human tooth and nail. Simultaneous measurement of refractive index and thickness of multilayer tissue are also demonstrated.

Refractive index tomography of turbid media by bifocal optical coherence refractometry

“…Tearney et al [14] introduced a suitable focus-tracking method that uses optical coherence tomography (OCT) to track the focal-length shift that results from translating the focus of an objective along the optical axis within a medium. They used it to determine the refractive index of skin tissue in vivo and it has been further developed by others for application to tissue [15][16][17]. The method is inherently somewhat time consuming, as it relies on a sequence of measurements at each discrete axial displacement of focus and, therefore, is prone to sample motion artefacts.…”

“…The other broad class of methods of refractive-index measurement employs interferometry [13][14][15][16][17][18][19]. This class relies on the measurement of the reference-arm optical pathlength required to match the variations in the sample-arm optical pathlength, and must include a means of decoupling the refractive index and the physical length, the product of which gives the optical pathlength.…”

Average refractive index of tendon as a function of water content

“…5. An average value of k sdry was 0.323 ± 0.003 (mean±one-half of the range; 3 samples), and, consequently, the average volume fraction of water for fascicles in the native state can be estimated as 0.677 ± 0.003 [see (5)]. Taking 0.677 ± 0.003 for C w and 1.34 for the specific gravity ρ dry of the dry tissue [31], we may estimate the average weight water content for the samples in the native state as 61 ± 0.3 wt %.…”

“…One of the optical parameters that can be directly measured for biological tissues is the average refractive index of the tissue [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. In the literature, one can find estimates of the average refractive index for many types of tissues (cornea, sclera, dermis, epidermis, brain tissue etc.…”

Simultaneous Measurement of Thickness and Refractive Index of Transparent Material Using a Collimated Beam Having a Finite Radius

“…[2][3][4][5][6][7][8][9][10] OLCR 은 Michelson 간섭계를 기반으로 하는 고정밀 간섭계로써 두 광속 간의 간섭을 이용하는 비접촉, 비파괴 측정 기법이다. [11] OLCR은 광대역 광원을 이용하기 때문에 두 광속의 광 경로 차가 가간섭거리(coherence length) 이내인 경우에만 간섭 무 늬가 관찰되므로 고정밀 측정이 가능하고, 기준단(reference arm)의 주사 폭에 따라 넓은 측정 범위를 제공할 수도 있다.…”